This invention relates to the maintenance of automobile internal combustion engines and, more particularly, to a method and apparatus for flushing brake systems on such engines.
Automobiles, motorcycles, and numerous other vehicles typically use hydraulic brake systems for slowing and stopping. These hydraulic braking systems were first introduced in the mid-1920s.
A typical hydraulic brake system contains a pressurizing device, which is referred to as the master cylinder. When the vehicle""s brake pedal is depressed, a sealed plunger within the master cylinder pushes against a volume of brake fluid causing the fluid to flow under pressure through brake activation devices. Some examples of such devices are proportioners and anti-lock brake sensors. Almost instantaneously after depression of the brake pedal the pressure from the master cylinder pushes against pistons in the wheel cylinders on the vehicle. These wheel cylinders apply pressure to brake shoes or pads forcing them against either a metal brake drum or disc shaped rotors.
Some common enemies to the typical braking system are the system contaminants of air and moisture in the system. Any air in the system will compress and prevent the applied pressure from the master cylinder from being properly transferred to the wheel cylinders. Any moisture in the brake fluid will boil under the heat from the friction generated between the stationary brake shoes or pads and the moving metal rotor or drums. Any such boiling results in steam which can interfere with the direct transfer of pressure from the brake pedal to the wheel cylinder in much the same manner as results from air contamination. The presence of either air or steam within the brake system can result in severe safety concerns because the vehicle may not be able to stop as quickly as designed.
Similar air and moisture problems can occur in manual transmission clutch systems because these systems are operated by very similar hydraulic systems as are brake systems. In fact, often the same fluid is used.
The components in both brake and clutch systems are manufactured of such materials as rubber, aluminum, cast iron, steel, and brass. These materials may deteriorate as the result of exposure to moisture (i.e., may rust, decay, etc.). Further, movement of the master cylinder, hydraulic reactionary devices, and wheel cylinders create wear particles that eventually contaminate the brake fluid making it necessary to replaced the existing old fluid with new brake fluid.
A very popular method of flushing and bleeding brake systems is the pressurized method. This is accomplished by bleeding the brake system under pressure to remove the old fluid. The pressurized method is the only way to properly flush most modern anti-lock brake systems.
Other prior art methods exist in which a vacuum is applied to the bleeder valve of each wheel cylinder and the fluid is pulled out of the system. This method is unsatisfactory because contaminating air oftentimes is sucked in around the loosened bleeder valve. Additionally, the vacuum method is not strong enough to open some anti-lock brake systems to ensure removal of the old fluid. Because of these disadvantages, pressurized flushing remains the most popular method of changing out brake fluid.
The apparatus most commonly used to accomplish pressurized flushing bleeding of brake or clutch systems has been around for many years, and is commonly referred to as a xe2x80x9cbrake-bleeder ball.xe2x80x9d The prior art brake-bleeder ball is essentially a tank consisting of two halves or pieces arranged one on top of the other. These two halves of the tank are divided by a flexible diaphragm, the outer edges of which are clamped between the edges of the two halves of the tank. These two halves are bolted together to clamp the outer edge of the diaphragm. The bottom half of the tank has an opening to allow for the entry of pressurized air. The upper half of the tank has two openings. The diaphragm dividing the halves is not taut, rather it is loose so that it may be pushed towards the bottom of the tank when the upper half of the tank is filled with the new fluid. The first opening in the upper portion is capped once the new fluid is loaded. After replacing the cap, the second opening in the upper portion is used to expel fluid from the tank under pressure when the lower half of the tank is pressurized due to the introduction of air through the opening in the bottom half compartment. More specifically, the diaphragm is pushed by air pressure in the bottom half of the tank towards the upper half of the tank to expel fluid. The new fluid expelled from the upper half of the tank is used to flush and bleed a brake or clutch system under pressure.
In order to refill the prior art brake bleeder ball, the user is required to first manually force the flexible diaphragm towards the bottom half of the tank using a blunt object. This is done so that the diaphragm conforms to the bottom half of the tank in such a manner as to allow room for the new brake fluid to be received by the tank. If the diaphragm is not pushed down in this manner and is left inverted towards the top half of the tank, there is no capacity for adding the new brake fluid. After the diaphragm is in position, new brake fluid is manually poured in the tank using a funnel. Once the tank is filled, the prior art bleeder-ball system is ready to be used for pressurized flushing.
However, using this prior art bleeder-ball system for pressurized flushing and bleeding has numerous disadvantages.
The primary disadvantage of such a system is that it allows for contamination of the new brake fluid. Brake fluid is extremely hydroscopic, meaning that it will absorb large amounts of moisture directly from the air it comes into contact with. Therefore, it is extremely important that the new brake fluid be allowed as little contact with air as possible. When the diaphragm is pushed down and new brake fluid is poured into the tank, there is a high level of contact between the air and the new fluid. Additionally, because there is no way for the user to know how much new fluid is left in the tank after each brake flush it is impossible to know when the tank is empty enough to accommodate the entire contents of a new fluid container purchased in the marketplace. Marketed containers of new fluid are sealed from contact with the air and are intended to remain that way until and use. However, because there is no way to tell when the prior art tank is almost empty, users often fill the tank earlier than is necessary to avoid the unfortunate situation of running out of pressurized fluid in the middle of the flushing process. As a result, users often will fill the tank earlier than is necessary, leaving partially filled, air exposed and unsealed containers on the shelf which allow new fluid to absorb undesirable moisture. In addition to this disadvantage of leaving around half emptied containers of fluid, there is also the risk that the unknown fluid level in the tank will cause the user to run out of fluid in the middle of the flushing process. This may result in the waste of large quantities of fluid and cause additional air contamination within the brake system. Further, the aforementioned use of a blunt object to push the diaphragm down can also cause the real possibility of puncturing the diaphragm causing contaminating air to bubble within the new fluid being administered to the brake system while under pressure. Other sources of contamination in such prior art systems result from the pouring of the fluid into a funnel for insertion into the container, the splashing of the fluid within the air filled tank after it leaves the funnel, and the air allowed into the tank every time the fill cap is removed and reinserted. As already mentioned above, contamination of the brake fluid can cause the brakes to become dangerously nonresponsive to compression of the brake pedal.
Another source of contamination is from shards, threads, or other solid impurities materials that may fall into the tank each time the filling plug is removed and then installed again. Similar impurities may also be introduced into the tank by the blunt object used to push the diaphragm back into position. Solid impurities can destroy the effectiveness of the brake system and lead to unnecessary repairs.
Because contamination by air, moisture, or solid impurities in brake fluid can dangerously compromise the effectiveness of a vehicles brakes, it is imperative that new fluid used to flush remain pure throughout the process.
It is therefore an objective of the present invention to provide a method and apparatus for flushing and bleeding vehicle brake systems that is simple and effective.
More particularly, it is an object of the present invention to provide a method and apparatus for flushing and bleeding the brake system of a vehicle in a manner in which the new brake fluid used is not exposed to air or other impurities.
It is a further objective of the present invention to provide a method and apparatus for indicating when the new fluid remaining within the tank is close to being empty and needs refilling.